Service life extension of a local area on a perforated grid of front flap of a high-speed aircraft air intake

Аuthors

Ordin A. V.^1*, Ripetskiy A. V.^2**, Ivanov A. O.¹

1. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
2. ,

*e-mail: alexey_ordin@mail.ru
**e-mail: a.ripetskiy@mail.ru

Abstract

The subject of the inquiry is a problem of high-speed aircraft service life extension as one of the central problems of modern aviation. The author deals with a problem of short life time (less than 100 flight hours) of a high-speed aircraft air intake panel. A high-speed aircraft air intake panel has been analyzed with relation to fracture pattern, aircraft operation conditions, statistics of operating hours prior to fracturing.
Service life extension of a local area on a perforated screen of a high-speed aircraft air intake.
The real cause is air intake nose part torsion motion which appears as a result action stalling of boundary layer on an air-intake structure.
The common version that air intake perforated screen damage is caused by dynamic pressure in Mmax mode is shown to be baseless. The real cause is air intake nose part torsion motion which appears as a result action of boundary layer stalling on an air intake structure.
Measurements of vibration overloads and stress in an air intake nose part (place of forward panel attachment) show that significant oscillations are set up in descent (with an elevated angle of attack). Frequency tests of an air intake nose part have shown that torsion motion of an air intake nose part (f=170Hz) excites torsion motion of a front screen whereby a loading diagram of a perforated screen has been suggested in the article. For practicing perforated screen repair vibration tests have been conducted on a full-scale panel and subscale demonstrators corresponding to perforated screen parameters (material, thickness, and configuration). Fractures appeared as a result of conducted tests correspond with service fractures. Repair works have been performed by welding with specially selected additives.
Tests of overhauled samples have shown service life extension of the repaired with additives samples by 5-10 times in comparison with original samples which provides more than 2000 hours of service life for a front screen of an air intake (takeoff and landing).

Keywords:

CALS, service life, acoustic loads, , air intake nose panel, statistics of operating hours

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